An RCMP ship dubbed St. Roch II set out from Vancouver Saturday on a brave attempt to re-trace one of Canada's most historic voyages, through the Northwest Passage.

Over the next six months it will follow the route of the original St. Roch, which in 1940 became the first to open the treacherous Arctic route.

The crew also hopes to locate the graveyards of two British ships, which 150 years ago entered the ice-bound waterway and have never been found.

The RCMP's Nadon has been fashioned into the St. Roch II for this journey. The ship left Vancouver harbour Saturday at about 5 p.m. PT.

St. Roch II hopes to make a 22,000 nautical mile journey around North America. Sgt. Ken Burton, who will captain the ship, says getting caught in ice in Canada's Northwest Passage is a real possibility.

"We're dealing with ice in the Arctic, we're dealing with North Atlantic storms, hurricane season in the Caribbean, and it's uphill all the way from the Panama," Burton said.

The original St. Roch set sail from Vancouver, led by the RCMP's Sgt. Henry Larsen. It was a secret Second World War mission to assert Canadian sovereignty over the Arctic islands.

The trip took two years. Larsen and his crew became the first to complete the voyage through the Northwest Passage from west to east. Later, they were the first to circumnavigate North America.

Before Larsen, every other attempt failed, and most ended in disaster.

The most famous was in 1845, when explorer John Franklin with two ships and a crew of 129 men left England looking for a northern trade route to China. Only a few human bones from the expedition have been found, but no sign of the ships. There have been 30 expeditions to find the wreckage.

Today's St. Roch II is equipped with state of the art sonar imaging and underwater cameras, equipment that will help in the search for the Franklin vessels. But no amount of technology, bravery, or determination can guarantee that this 20-metre aluminium catamaran will win in a battle against ice, water, and wind.

A teacher will be on board the vessel, transmitting history lessons and photographs to an official website. The expedition hopes to raise funds for restoration of the original St. Roch, which is housed at the Vancouver Maritime Museum.